Suppress checkstyle for lombok's val using SuppressionXpathFilter

Question

I am using lombok's val to specify the final variables in my code. The checkstyle rule for FinalLocalVariable reports any val variable as non-final. I am trying to write a custom suppress.xml to suppress this check for any val field. Currently, my suppression.xml looks like this

<?xml version="1.0"?>
<!DOCTYPE suppressions PUBLIC
    "-//Checkstyle//DTD SuppressionXpathFilter Experimental Configuration 1.2//EN"
    "https://checkstyle.org/dtds/suppressions_1_2_xpath_experimental.dtd">
 <suppressions>
<suppress-xpath 
        checks="FinalLocalVariable" query="//VARIABLE_DEF[./TYPE/IDENT[@text='val']]"/
</suppressions>

I have generated the AST tree for the class that has the val fields, here is the part where val is declared

`--SLIST -> { [32:96]
    |       |--VARIABLE_DEF -> VARIABLE_DEF [33:4]
    |       |   |--MODIFIERS -> MODIFIERS [33:4]
    |       |   |--TYPE -> TYPE [33:4]
    |       |   |   `--IDENT -> val [33:4]

My idea was to specify that any variable definition of identity val should be ignored for this exact check. I have read the checkstyle's documentation for SuppressionXpathFilter and I cannot find what my issue is as the checkstyle keeps reporting that the variable should be declared final. Any help would be much appreciated.

Answer 1

You need to address the IDENT child node of the VARIABLE_DEF with the suppression query:

query="//VARIABLE_DEF[./TYPE/IDENT[@text='val']]/IDENT"

For the following source code:

class C {
    void m() {
        val a = 3;
    }
}

with the following checkstyle config:

<?xml version="1.0"?>
<!DOCTYPE module PUBLIC
        "-//Puppy Crawl//DTD Check Configuration 1.3//EN"
        "http://www.puppycrawl.com/dtds/configuration_1_3.dtd">
<module name="Checker">
    <property name="fileExtensions" value="java"/>
    <module name="TreeWalker">
        <module name="SuppressionXpathFilter">
            <property name="file" value="suppressions-check.xml"/>
        </module>
        <module name="FinalLocalVariable"/>
    </module>
</module>

using this suppression filter file:

<?xml version="1.0"?>
<!DOCTYPE suppressions PUBLIC
        "-//Checkstyle//DTD SuppressionXpathFilter Experimental Configuration 1.2//EN"
        "https://checkstyle.org/dtds/suppressions_1_2_xpath_experimental.dtd">
<suppressions>
    <suppress-xpath checks="FinalLocalVariable" query="//VARIABLE_DEF[./TYPE/IDENT[@text='val']]/IDENT"/>
</suppressions>

Checkstyle won't report any error.